Obesity is associated with risks for several serious diseases, and excess visceral fat is known to be associated with risks for metabolic abnormalities. The literature suggests that women who do not return to pre-pregnancy body weight within 6 to 12 months after delivery are more likely to gain more weight in future years, and therefore have increased risk of becoming obese. Also, women who have given birth tend to have greater total fat and visceral fat compared to women who have not given birth, independent of body weight. Additionally, sleep deficiency during postpartum, likely related to caring for the infant, is common. Limited information in the literature suggests that short sleep and lower sleep efficiency in postpartum are associated with greater weight retention and higher adiposity at postpartum, independent of gestational weight gain and pre-pregnancy weight status. African American women are more prone to postpartum weight retention than White women. In addition, epidemiologic studies show that African Americans have shorter total sleep time and poorer sleep quality than Whites, and that short sleep is associated with greater likelihood of being obese in African Americans than Whites. Collectively, it is plausible that sleep deficiency contributes to the differences between African American and White women in postpartum weight and fat. The main goal of the proposed study is to examine whether differences in sleep during postpartum exist, and whether sleep deficiency affects weight and fat changes in postpartum differently between the two groups. African American and White women will be recruited, with baseline measurements occurring 6-8 weeks postpartum and follow up measurements at 4, 6, 9, and 12 months postpartum. Body weight will be measured at each time point, and body fat will be measured by dual energy-X-ray absorptiometry at 6-8 weeks and 6 and 12 months postpartum. Sleep will be assessed by actigraphy and validated questionnaires at each time point. Potential confounding variables, such as sociodemographic background, depression, self-esteem, stress, physical activity, dietary intake, breast feeding, and smoking status, will also be assessed. The specific aims of this study are: 1) to compare body weight, body fat, and sleep parameters between African American and White women from early to 12 months postpartum; 2) to determine the associations between sleep parameters and changes in body weight and body fat during the first year after delivery, and to explore whether the associations differ between African American and White women. Sleep parameters will include sleep duration and variables of sleep fragmentation and quality. The proposed study will be one of the first to comprehensively examine the effects of sleep deficiency, by assessing multiple sleep parameters in a longitudinal study, during postpartum on changes in body weight and body fat among both African American and White women. Results of this study will help examine the role of an understudied risk factor that may contribute to the differences in obesity-related health outcomes between African American and White women.